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(librep.info)Read Syntax

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Read Syntax
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   As previously noted the Lisp reader translates textual descriptions
of Lisp objects into the object they describe (source files are simply
descriptions of objects). However, not all data types can be created in
this way: in fact the only types which can are numbers, strings,
symbols, cons cells (or lists) and vectors, all others have to be
created by calling functions.

   Single line comments are introduced by a semi-colon character (`;').
Whenever the Lisp reader encounters a semi-colon where it's looking for
the read syntax of a new Lisp object it will discard the rest of the
line of input. Block comments are also supported, introduced by the
string `#|' and terminated by `|#'.  Note: Comment Styles.

   The "read syntax" of an object is the string which when given to the
reader as input will produce the object. The read syntax of each type
of object is documented in that type's main section of this manual but
here is a small summary of how to write each type.

Numbers
     A number is number written as an integer--decimal, octal (when the
     number is preceded by `#o') or hexadecimal (when the number is
     preceded by `#x')--or a decimal rational or floating point value.
     An optional minus sign may be the first character in a number. Some
     examples are,

          42
              => 42
          
          #o177
              => 127
          
          #x-ff
              => -255
          
          3/2
              => 3/2
          
          1.23
              => 1.23

Strings
     The read syntax of a string is simply the string with a
     double-quote character (`"') at each end, for more details see
     Note: Strings.

          "This is a string"

Cons cells
     A cons cell is written in what is known as "dotted pair notation",
     an opening left-parenthesis, followed by the read syntax of the
     first object, followed by a dot, then the second object, and
     finally a closing right-parenthesis. For example:

          ("car" . "cdr")

Lists
     The syntax of a list is similar to a cons cell, but the dot is
     removed and zero or more objects may be written:

          (0 1 2 3)
          
          ("foo" ("bar" "baz") 100)

     The second example is a list of three elements, a string, an inner
     list and a number.

Vectors
     The read syntax of a vector is similar to that of a list, but with
     square brackets instead of parentheses,

          [0 1 2 3]

Symbols
     The read syntax of a symbol is its name, for example the read
     syntax of the symbol called `my-symbol' is,

          my-symbol